Drugs of varying types, bronchodilators and steroids being two examples, have been available in pressurized aerosol canisters, suited when manually actuated to deliver a small metered pulse of the drug, typically for administration into the opened mouth of the user. Simple dispensing devices are available to hold the canister, forming what is generally identified in the trade as an inhaler, thereby allowing the discharge as a misted spray to be accurately aimed into the user's open mouth. Many drugs however are intended to reach the user's lungs via the air passageways from the mouth, and misted sprays delivered from close range into the mouth largely tend to hit the inside mouth surfaces and become absorbed thereon, and thus never reach the lungs. The overall efficiency of any drug administered in this manner thus drops.
One form of inhaler has a tubular mouthpiece that can be held in the user's mouth, the interior of the mouthpiece defining a passageway somewhat concentrically around the spray discharge. This inhaler arrangement contains and more accurately directs the spray discharge into the mouth and further allows the user to breath deeply simultaneously when the spray enters the mouth. Clearance spaces provided in the inhaler allow for this breathing air flow via the inhaler to the mouth. Such inhalers help mix the combined inhaled air and misted drug, but yet are not very efficient as much of the sprays still strikes and remains on the user's mouth surfaces.
This is due to the close proximity of the actual exit point of the spray from the canister/inhaler and the user's mouth, whereby the high velocity misted but nonetheless large spray droplets of the discharged drug cannot navigate the nearby abrupt turns of the user's air passageways without striking and being absorbed thereon.
To overcome this drawback, some dispensing devices now provide a greater separation between the actual exit point of the spray from the canister/inhaler and the user's mouth, to allow the mist droplets to admix with and become more thoroughly atomized within the moving air. This greatly increases the percentage of the dispensed drug that reaches the user's lungs.
U.S. Pat. No. 4,470,412 illustrates a basic dispensing device inhaler with a tubular mouthpiece and structure for holding the drug canister, with the metered spray discharge being directed through the mouthpiece and into the user's mouth. The patent further illustrates an example of an extender device usable with this basis inhaler, comprised basically as a fixed tube having structures at its opposite ends suited to offer a separable connection to the inhaler mouthpiece and a different mouthpiece for the user's mouth. The hollow tube body increases the separation between the canister/inhaler spray exit point and the user's mouth, while defining a constrained flow path for the spray droplets, allowing for longer common admixture time between the drug and moving air, for increased drug atomization and improved efficiency in drug administration to the user's lungs.
However, despite the possibility of improved drug administration, extender devices find limited use away from the medicine cabinet, except for the more critically suffering patients, as they are too large for convenient portable use.
U.S. Pat. No. 4,484,577 illustrates another dispensing device that has a fixed tubular extender with a mouthpiece at one end and a bellows at the opposite end, and with midpoint structure suited to hold a drug canister to discharge the drug into the bellows. When using the dispensing device, the user's mouth would be positioned over the mouthpiece and the bellows would be fully expanded, whereupon the user would inhale simultaneously with the drug being discharged into the bellows, to collapse the bellows and draw the combined bellows air/drug into the user's lungs via the mouth. While this device can increase the efficiency of drug delivery to the user's lungs, the device is difficult to use with the needed inhalation to collapse the bellows. Further, the collapsible bellows can be quite fragile, negating much of the appeal its compact size might offer for portable use.